Only once, and suprsingly I'm not embarrased, never was.
I was walking in a mall, feeling incredably weak, next thing I know I'm lying on the floor with shit running down my legs, and a dude holding my back off the floor.
I cant recall passing out but as soon as I did my anus let loose. It drew a crowd, but I got the guy to escort me to the bathroom as soon as I regained consciousness, and cleaned myself up as much as I could.